Tension oleo strut



F. E NY TENSION OLEQ STRUT Filed Juiy 2. 1935 Sept. 7, 1937.

2 Sheets-Sheet l INVENTOR.

ERNY.

ATTO EYS.

Sept. 7, 1937.

F, ERNY TENSION OLEO STRUT Filed July 2, 1955 2 Sheets-Sheet 2 mink" IPatented Sept. 7, 1937 UNITED [STATES 2,092,644 TENSION OLEO STRUT FranhErny, Kenmore, N. Y., assignor, by mesne assignments, to Curtiss-WrightCorporation, a corporation of New York Application July 2, 1935, SerialNo. 29,459

3 Claims.

This invention relates to aircraft landing gears, an?h to a shockabsorber suitable for use there- W1 absorbing devices.

An object of the invention is to provide a landing gear for an aircraftadapted for lateral swinging with respect to the aircraft.

Afurther object is to provide a tension type of shock absorber unitconnecting the strut and the aircraft.

A further object is to draulic shock absorber upon by gravity.

Further objects will be apparent from a reading of the subjoinedspecification and claims, and from an examination of the accompanyingdrawings, in which similar-numbers indicate similar parts, and in which:

Fig. 1 is a side elevation of the forward part of 15 an aircraftembodying the landing gear of this invention;

Fig. 2 is a diagrammatic front elevation showing a portion of thefuselage and landing gear;

I Fig. 3 is an enlarged front elevation of the tension shock absorberstrut; I

Fig. 4 is an enlarged section through the operation mechanism of theshock absorber strut; and Fig. 5 is a section on the line 55' of Fig. 4.In referring to the drawings, I 0 indicates an air- 5 craft fuselagehaving a skeleton framework I I,'the

fuselage being conventionally provided with wings, power plant and thelike. To the lower outer corners of the fuselage skeleton II, a mainlanding gear strut I2 is pivoted, as at I3, this strut extendingdownwardly and outwardly to carry a stub axle I4 on which a wheel I5 iscarried for ground contact. The strut I2 may have a rearwardly extendingprojection I6 likewise pivoted to the fuselage skeleton through whichextension drag loads on the landing gear are as-, sumed. The strut I2also is provided with an inward extension I! carrying an eye I8, throughwhich a bolt I 9 passes. Centrally of the fuselage, on a pivot 20, ismounted the upper end of the shock absorber strut 2 I, the lower end ofthe strut 2I being pivoted upon the bolt I9. Fig. 2 shows in dottedlines the position of the landing gear in the flight position, whereinthe weight of the strut I2 and its associated elements causes thelanding gear to droop and to collapse the shock absorber strut 2| to itsshortest length. Upon landing impact, the strut I2 is moved upwardly andoutwardly as shown in solid lines in Fig. 2, tending to elongate thestrut 2 I.

Figs. 3 and 4 show the strut 2| in-detail. The strut comprises "a pistonrod 22 screwed at its lower end into an abutment fitting 23 having aneye 24 for engagement with the bolt I9. Onan abutment surface 25 of thefitting 23, a'rubber disc 26 rests, this being superimposed by a metalwasher 21 for engagement, upon collapsing of the strut, with the lowerextension'28 of a cylinder 29. The extension 28 is provided with a bore30 through which the piston rod 22 passes, the extension 28 beingprovided with'packings 3| and a packing nut 32 to seal the piston rodwithin the bore 30. The piston rod, at its upper end, is provided withan integral piston 33, theperiphery of which engages the walls of thecylinder 29. The top of the cylinder 29 is threaded as at 34 forengagement with a top closure 35, said closure being sealed and beingprovided at its upper end with an eye 36 for engagement with the pivot20 on the aircraft fuselage. The piston rod-22 is counterbored as at 3'!to receive the end of a metering pin anchored to the top of the closure35. The piston 33 is formed with a recess 39 in its upper face, theedges of the recess. being threaded to receive a nut 40, thus providinga cavity within the piston head within which a flap valve 4| is adaptedto seat. The nut 40 is centrally perforated with a hole of considerablygreater diameter than that of the largest portion of the metering pin38,

the valve M is provided with a central hole of a diameter only slightlyin excess of that of the 10 central bore of the nut 40.

metering pin 38. Openings 42 are provided from flap valve is obtainedwhen the piston is pushed upwardly within the cylinder, by virtue offluid above-the piston impinging upon the valve and pressing it againstthe lower wall of the cavity.

15 However, in such an action, the fluid has relatively free flow fromabove the piston to below the piston. Upon extension of the shockabsorber, fluid below the piston must pass thereabove, through theopenings 42, whereupon the flap valve is 20 pressed against the upperwall of the cavity 39,

closing off a large portion of the opening in the nut 40 and causing arestriction in the path of the fluid, thereby damping the extension ofthe shock absorber strut. It is this latter condition which 25 accrueswhen the landing gear is subject to ground impact, so that landingshocks are adequately, but non-reactively, absorbed. When the aircrafthas completed a landing, the edges of the piston 33 abut against theupper faces of the lower end 3 of the cylinder 2|, making a solidconnection.

35 washer 21 When the aircraft is in flight, the landing gear will droopdownwardly so that the upper edges of the piston approach the loweredges of the closure 35. However, they do not abut, since the will havecome into contact'with the lower face of the cylinder extension .28. Therubber ring 26 will act as a buffer to prevent sudden shocks when thelanding geardroops to itsjlowermost position. i 'fr' For facility inassembling, the nut when screwed into the head of the piston 33is'locked from looseness by the use of a spring ring 43 seating withinan annular groove within the inner face of the nut 40, said spring ringhaving an extension 44 adapted to register with'notches 45 and 46 cutrespectively in the upper face of the nut 40 and in the upper part ofthe piston 33.

To minimize leakage of contained fluid from the cylinder, through thebore 30, 1 form an annulus 41 within the bore 30 but above the packing3|, this annulus being connected by passages 48, 4

and 50 formed in the wall of the cylinder 25, to the cylinder interiorabove the highest piston position. Normally, the flt of the piston rod22 in the bore- 30 is a close running flt, so that a relatively smallamount of fluid will leak downwardly between the piston rod and thebore. However, when the shock absorber strut is subjected to landingimpact, the pressure below the piston is built up to a very high degree,whereas the pressure above the piston is relatively low. Therefore, anyleakage between the piston rod 22 and the bore 30 will collect in theannulus 41, and as the pressure builds up to a point greater than thepressure above the piston, fluid will be by-passed through the passages48, 49, and 50 to the upper part of the cylinder. To cavity within thecylinder closure 35 will ordinarilybe under atmospheric pressure Thisposition for the and provides a clearance space into which a certainamount 0! oil may enter when such oil is displaced by the piston rod 30as it enters the cylinder.

A flller plug is provided in the closure 35 by which the proper amountof hydraulic fluid may be placed within the strut.

The metering pin 38 may be tapered in part to provide varying degrees ofhydraulic resistance as the shock absorber strut operates.

While I have described my invention in detail in its present preferredembodiment, it will be obvious to those skilled inthe art, afterunderstanding my invention, that various changes and modiflcations maybe from the spirit or scope thereof. I aim in the appended claims tocover all such modifications and changes.

What is claimed is: v

1. A tension oleo strut for aircraft landing gears comprising incombination a cylinder having a reduced diameter portion at its outerend, a piston rod reciprocable portion, a packing in said reduceddiameter portion for sealing said piston rod, a piston on said rod forengagement with said cylinder, said piston having an openingtherethrough, valve means organized for substantially closing saidopening upon movements of said piston rod out of said cylinder and foruncovering said opening upon movement of said piston rod into saidcylinder, and a metering pin of varying cross section along its length,carried by said cylinder and engaging within said opening.

2. A tension oleo strut for aircraft landing gears comprising incombination a cylinder, a piston rod reciprocable through the end of thecylinder, a packing in said end for sealing said piston rod, a piston onthe rod for engagement with the cylinder walls, said piston having anopening therethrough, valve means organized for substantially closingsaid opening upon movement of said piston rod out of said cylinder andfor uncovering said opening upon movement of said piston rod into saidcylinder, and a metering pin of varying cross section along its lengthcarried by said cylinder and engaging within said opening, said valvemeans embracing said pin.

3. In a tension oleo strut comprising a cylinde a piston slidabletherein, and a hollow piston rod extending from the cylinder; said rodhaving a duct establishing communication between opposite sides of thepiston, a metering pin fixed to the cylinder engaging within the rodhollow, a metering valve embracing the pin'so loosely as to permit offluid flow between the pin and the edge of the opening through which thepin passes, said valve being movable with and with respect to the pistonand being carried thereby, and opposed valve seats in the piston uponone or the other of which said valve is adapted to seat, said valverespectively engaging one or the other of said seats and restrictingfluid flow through the piston when the piston rod is withdrawn from thecylinder and permitting free fluid flow through the piston when thepiston rod is pushed into the cylinder.

FRANK ERNY.

made therein without departing through said reduced diameter

